If you play dead in order to kill or capture an enemy in a war scenario, you are committing a war crime according to the Geneva Convention.

State Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts (Protocol I), 8 June 1977.PROHIBITION OF PERFIDY
Article 37 [ Link ] — Prohibition of perfidy
1. It is prohibited to kill, injure or capture an adversary by resort to perfidy. Acts inviting the confidence of an adversary to lead him to believe that he is entitled to, or is obliged to accord, protection under the rules of international law applicable in armed conflict, with intent to betray that confidence, shall constitute perfidy. The following acts are examples of perfidy:
(a) the feigning of an intent to negotiate under a flag of truce or of a surrender;
(b) the feigning of an incapacitation by wounds or sickness;
(c) the feigning of civilian, non-combatant status; and
(d) the feigning of protected status by the use of signs, emblems or uniforms of the United Nations or of neutral or other States not Parties to the conflict.
2. Ruses of war are not prohibited. Such ruses are acts which are intended to mislead an adversary or to induce him to act recklessly but which infringe no rule of international law applicable in armed conflict and which are not perfidious because they do not invite the confidence of an adversary with respect to protection under that law. The following are examples of such ruses: the use of camouflage, decoys, mock operations and misinformation.